How does one go about calculating the temperature of your batch sparge liquor in Beersmith? If I click on the checkbox for batch sparge and say I want to sparge at 170F it tells me to batch sparge at 170F, instead of whatever temperature would bring the temp to 170. If I add a step to the mash to find out sparge temp, it calculates the temp assuming the mash liquor is still in there and thus gives a number too high.

You can use the TOOLS, ADJUST MASH tool. This will calculate the needed infusion to reach mashout or decoction rests. If you drain out some of the liquid then keep trac of the amount and you will know how much liquid is still in the mash tun. You then enter this volume in the current mash conditions, water volume and it will calculate the proper volume to infuse and you can set the infusion temperature to something else other than 212F if desired too. You have full control over every aspect of infusion. The one thing you have to be careful about is having enough room in the mashtun.

I know you've already found your answer, but I just thought I'd mention... If you do a mash out, the sparge temp is always the same since your grain bed will already be up to temp - this is one of the reasons I choose to do a mash out, it makes the sparge temp a no-brainer. Beersmith does the mash out calculation just fine, and then I just eyeball it to split up my sparge into two roughly equal batches.